Integrated steering and braking control for vehicle trajectory tracking under extreme conditions considering road adhesion coefficient—A dynamic weight coefficient allocation strategy

Under extreme operating conditions, coordinated steering and braking control is critical for vehicle safety. However, variations in road adhesion coefficients lead to differences in tire force utilization limits, necessitating dynamic adjustment of steering and braking control weights. To address this challenge, this study proposed a trajectory tracking control method with adhesion-aware dynamic weight allocation for steering and braking. Firstly, a lateral-longitudinal coupled vehicle dynamics model is developed, integrating front wheel steering angle and braking deceleration as control inputs. Secondly, a unified MPC framework is designed for trajectory tracking, where fuzzy logic dynamically adjusts the weighting coefficients between control effort and tracking error in the cost function based on real-time vehicle speed and reference trajectory curvature. Furthermore, to account for the influence of road adhesion coefficients on tire force utilization efficiency and driving stability, the mathematical model of weight coefficient correction is established. This two-stage adaptation mechanism integrates fuzzy logic and empirical rules based on mathematical models, enhances steering and braking maneuverability and trajectory tracking accuracy while rigorously guaranteeing stability across the adhesion-variant operating envelope. Simulation results demonstrate that the proposed controller achieves adaptive redistribution of steering and braking authority across different road surfaces, significantly improving handling stability and trajectory tracking precision compared to fixed-weight benchmarks. This method enhances the safety envelope of autonomous vehicles in adhesion-constrained emergency scenarios.